Bump librt from 0.8.1 to 0.9.0

Bumps [librt](https://github.com/mypyc/librt) from 0.8.1 to 0.9.0.
- [Commits](mypyc/librt@v0.8.1...v0.9.0)

---
updated-dependencies:
- dependency-name: librt
  dependency-version: 0.9.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -8,7 +8,7 @@ dependencies = [
     "difflib-parser==2.1.1",
     "git-autograder==6.8.0",
     "gitpython==3.1.46",
-    "librt==0.8.1",
+    "librt==0.9.0",
     "pygments==2.20.0",
     "pytermgui==7.7.4",
     "pytz==2026.1.post1",